ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Breakpoint cluster region (BCR)-ABL is the protein product caused by the t(9;22)(q34;q11) translocation (also known as the Philadelphia chromosome) is most commonly found in CML, but also accounts for 20–40% of adult B ALL and 3–5% of childhood B ALL cases (34, 35).